Tag: stroke

In another confusing nutrition story that should be titled “is there anything left for us to eat?” recent research threw a curveball. Fish, a staple of the Mediterranean diet, as well as meat and eggs may be doing more harm than good thanks to a compound called trimethylamine-N-oxide (TMAO). TMAO is found in fish and produced in the body after eating meat and eggs. TMAO is linked to greater risk for heart attack, stroke and death; yet the research isn’t crystal clear. Is it time to give up fish meat and eggs or ignore the recent media headlines?

This post will cover:

TMAO: More than a Gut Reaction—What gives us higher TMAO levels?

TMAO and health?

The bottom line

TMAO: More than a Gut Reaction

Blood levels of TMAO are ~ 50 times higher after eating fish compared to eggs or beef. The human body absorbs intact TMAO like the kind found in fish, easily. However, the human body’s production of TMAO, after eating foods containing the essential nutrient choline (found in eggs and meat) and the compound l-carnitine (found in meat and pork and in much smaller quantities in chicken breast and dairy products), depends on the makeup of bacteria in your gut, kidney functioning and genetics.

In one study, regular meat eaters produced more TMAO than a vegetarian did after eating steak (which contains ~ 180 mg of l-carnitine). After wiping out their gut bacteria with antibiotics, the carnivores didn’t produce any TMAO after consuming 250 mg l-carnitine. The makeup of gut bacteria in the habitual meat eaters was presumably responsible for greater TMAO production compared to the vegetarian, yet this was a small study and we don’t know anything else about the participants’ diet. Was it the meat that altered gut bacteria or something else in their diet? After all, a steady diet of red meat may mean double cheeseburgers on white bread with regular servings of French fries and soda on the side. This isn’t exactly the diet you want for promoting good bacteria in your gut.

Another study found blood levels of TMAO were greater in those with a less diverse makeup of microbes and greater amounts of a less healthy type of bacteria (firmicutes), compared to one that is healthy (bacteroidetes). A diet higher in saturated fat will promote this environment.

While bacteria seem to influence TMAO production from l-carnitine, l-carnitine also influences the makeup of gut bacteria. A study in mice found those with their gut bacteria wiped out thanks to antibiotics produced a different makeup of bacteria in the gut after consuming l-carnitine while also doubling the risk of plaque buildup in their arteries.

Higher TMAO levels come from:

Eating fish

Less diverse array of gut bacteria and increased levels of bad versus good bacteria

Consuming l-carnitine (mouse study)

TMAO and Health

A few human studies found higher blood levels of TMAO were associated with greater risk for heart disease. However, all research isn’t pointing in the same direction. One study in over 300 patients found blood TMAO levels were not associated with heart attack or heart disease over the course of eight years, following the initial test for TMAO. However, TMAO levels were higher in those with diabetes, patients with metabolic syndrome and those with declining kidney functioning. Another study examined over 800 people between the age of 33 and 55 and found blood TMAO levels were not associated with clogged arteries, insulin resistance (this comes before type 2 diabetes) and inflammatory markers or negative changes in blood lipids suggesting TMAO levels might not contribute significantly to the progression of clogged arteries. However, this study shows TMAO levels were significantly lower than in previous research, showing an association between TMAO and heart disease.

TMAO is considered a risk factor for cardiovascular disease. In those with type 2 diabetes, higher TMAO levels are associated with greater risk for death, heart attack, heart failure and unstable angina (chest pain). Also, higher levels of circulating TMAO are associated with higher risk of death in those with chronic kidney disease and greater risk of certain cancers. Yet, there are several confounding factors. Fish is the primary culprit for higher acute circulating TMAO levels, yet fish-based diets are associated with reduced risk for heart disease. Also, levels of TMAO are dependent upon disease state and the makeup of gut bacteria. Therefore, at this time it isn’t entirely clear which came first – does TMAO cause disease or does TMAO increase due to disease?

The Bottom Line

The story on TMAO isn’t crystal clear, so there’s no reason to avoid fish, meat and eggs in an effort to decrease TMAO levels. All three of these foods are good sources of several nutrients important for health. Though processed red meats are linked to higher risk of colorectal and stomach cancers, when cooked appropriately (lower, moist heat for example) red meat can fit into a healthy diet and deliver important nutrients including iron, zinc and vitamin B12. Eggs are an economical source of protein and contain many nutrients and compounds that contribute to health including two antioxidants important for eyesight.

Though there is no reason to completely avoid these foods, you can alter your diet to help diversify gut bacteria and also increase the amount of good versus bad bacteria. Probiotic rich foods such as yogurt and kefir with live and active cultures, miso soup, tempeh and other fermented foods contain good bacteria. Fiber-rich plant foods (fruits, vegetables, legumes) are important food sources for bacteria to thrive in your body.

Disclosure: this post was sponsored by USFRA. All views are my own and backed by research.

If you are more confused than ever about dietary fats, you’re not alone. Can a high fat diet help you lose body fat? Which fat is best for heart health – butter, coconut oil or vegetable oil?

What is Cholesterol & Why is it Essential?
Cholesterol is an essential component of all cell membranes and a precursor to hormones, vitamin D and bile acids (needed for the digestion of fat). It is so important that your body regulates cholesterol balance to ensure your cells receive a continuous supply of cholesterol.

How does High LDL Contribute to Cardiovascular Disease?

Though cholesterol is critical for life, low density lipoprotein cholesterol, LDL cholesterol, is considered a risk factor for heart disease because excess LDL can lead to an increase in plaque buildup in your arteries. Think of this process like a garden hose with gunk stuck in it. The gunk interferes with water flowing through the hose. If too much debris gets in there, no water will flow through. Likewise, plaque in your arteries will decrease the amount of blood that moves through your arteries at one time and a complete blockage could lead to a heart attack or stroke. Now, this is a simplistic view, especially considering LDL isn’t just one particle but instead, several that contain different amounts of cholesterol. Some research suggests that smaller, more dense LDL particles are more artery clogging. However, in addition to particle size, total number of LDL particles and oxidation of LDL contribute to the disease process.

As LDL particles travel through the bloodstream, excess LDL particles can stick to artery walls (particularly walls that are damaged due to smoking, high blood pressure and other insults). Trapped LDL becomes oxidized and sets off an inflammatory cascade resulting in the development of plaque (gunk) stuck to arteries – atherosclerosis.

How Can I Lower my LDL Cholesterol?

Cholesterol in food has little effect on your blood cholesterol.

Years ago we were told to stay away from shrimp, eggs and other high cholesterol foods. Yet this advice wasn’t based on sound science – cholesterol in food has little effect on your blood cholesterol levels. So there is no need to take these nutrient-rich foods out of your diet. Shrimp is loaded with protein, and is a good source of iron plus it contains just 80 calories per serving. Eggs are also packed with nutrition – the whites are an excellent source of protein and the yellow color you see in the yolk is from antioxidants – plant compounds that protect plants from disease and protect your body from the damaging effects of free radicals, compounds that are essential but can cause damage as well.

Coconut Oil, Butter and Other Solid Fats are Not the Best Options

Man-made trans fats (partially hydrogenated oils) are the worst kind of fat you can eat. However, they should, finally, be making their way out of our food supply over the next few years. High levels of *saturated fat, the kind that is solid at room temperature like butter, increases HDL (the “good” cholesterol but not a target of therapy – doctors don’t focus on HDL levels because increasing HDL does not lower heart disease risk) and LDL cholesterol in the blood. In controlled diet experiments where saturated fat is replaced with polyunsaturated fat rich vegetable oils, risk of heart disease is reduced. Replacing saturated fat with monounsaturated fat, the kind found in olive oil, also lowers LDL but not to the extent that polyunsaturated fat does.

Coconut oil is popular and calorie for calorie it might be better for weight management than other fats. However, coconut oil raises our total, good and bad cholesterol levels. And therefore, it is not the best option for heart health.

Excess Carbohydrate Intake can Increase LDL

Overconsumption of carbohydrate-rich foods can also increase VLDL cholesterol (very low density lipoprotein). Foods with added sugars, in particular, are potent stimulators of VLDL production when the energy (calories) aren’t needed right away for energy or increasing glycogen stores (stored carbohydrate in your liver and muscle).

Best Fats for Your Heart

Nuts, seeds, avocados, olives and liquid oils are your bets for heart health. Oils with more polyunsaturated fat have a greater impact on LDL cholesterol than those rich in monounsaturated fat. Make sure you are choosing the right oil for the right cooking application. Many oils can’t stand high heat and they break down, damaging the structure (and function) of the oil.

Conclusion

Many factors contribute to high blood cholesterol levels, including genetics, overweight/obesity, inactivity, smoking, diabetes and age, making cholesterol management a multifactorial issue. Saturated fat increases LDL cholesterol but, as I’ll say over and over, we are all different and, people vary in their response to dietary saturated fat due to intrinsic differences in fat metabolism as well as other factors including obesity, insulin resistance and high triglycerides.

* There are differences in specific saturated fatty acids and their effects on blood cholesterol. Therefore, some foods high in saturated fat do not raise LDL cholesterol. Also, oils have a different array of vitamins (primarily vitamin E) and plant-based compounds that may be beneficial for heart health.

Fatty acids composition of oils taken from the USDA Nutrient Database.